Risk factors predict delayed seizure detection on continuous EEG in some

According to a retrospective study published in the journal Epilepsia Open, a number of risk factors have been shown to be associated with delayed continuous electroencephalogram (cEEG) seizure detection in critically ill patients.

Previous research has identified risk factors that have shaped current surveillance recommendations. Monitoring for at least 48 hours is recommended in comatose patients with a history of seizures, while 24-hour monitoring is recommended for most patients.

The aim of the current study was to identify additional risk factors that predict delayed seizure detection and to establish the optimal cEEG duration for a variety of patient subpopulations.

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They obtained EEG and clinical data from all patients who had a seizure during calendar year 2016 using the Cleveland Clinic’s cEEG database. Electronic patient records were reviewed and demographic data collected.

The mental status (ie, alertness, lethargy, drowsiness, and coma) of all patients was recorded at the time the cEEG was initiated. Alertness has been defined as “a fully awake and responsive state”. Lethargy has been described as a “hypersomnolent state with reduced alertness but excitable to minimal stimuli”. Stupor was defined as “unresponsiveness in which patients could only be awakened by violent, repeated stimuli.” Coma has been described as “an unawakenable unresponsiveness with no intelligible response to stimuli.”

A total of 2402 patients aged 18 and over met the inclusion criteria of the study. Among these individuals, 13.2% (316 out of 2402) experienced subclinical seizures. Of the participants who experienced a seizure, 79.4% (251 of 316) had their first seizure during 24-hour cEEG monitoring. Of the patients with seizures, 20.6% (65 of 316) had their seizures detected at 24 hours, 13.6% (43 of 316) had their seizures detected between 24 and 48 hours, and 7.0% (22 of 316) the seizures were recognized after 48 hours.

The study results showed that seizure detection increased linearly up to 36 hours of monitoring, with the probability of detecting seizures increasing by 46% with each additional day of monitoring.

Risk factors for significantly delayed seizure recognition included stupor (13.2% at 48 hours, P=0.031); lethargy (25.9%, P=0.013); lateralized periodic discharges (27.7%, P=0.029); generalized periodic discharges (33.3%, P=0.022); acute brain injury (25.5%, P=0.036); cerebral hemorrhage (32.8%, P=0.014); multiple concomitant cerebral hemorrhages (61.1%, p<0.001); altered mental status as the primary indication for cEEG (34.7%, p=0.001); and use of antiepileptic drugs at the onset of cEEG (27.8%, p<0.001).

The limitations of the study included the retrospective nature of the study, multiple neurological diagnoses, and different lengths of follow-up—patients with seizures compared to patients without seizures had a longer mean follow-up length. In addition, the statistical threshold for multiple comparisons was not adjusted.

The researchers concluded: “The above patient subpopulations are at risk of delayed seizure detection. For these high-risk patients, a longer cEG (≥48 hours) is recommended.”

Disclosure: None of the study authors have declared affiliations with biotech, pharmaceutical, and/or device companies.


Zawar I, Briskin I, Hantus S. Risk factors predicting delayed seizure detection on continuous electroencephalogram (cEEG) in a large sample of critically ill patients. epilepsy open. Published online December 16, 2021. doi:10.1002/epi4.12572

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